The invention relates to a tractor for trailers and devices equipped with a kingpin, used for transferring these in harbours, lorry terminals, industrial plants and elsewhere.
With the development of container transports the need to handle various kinds of trailers, transfer devices and the like has grown substantially at points of departure and destinations and junctions in the traffic. Examples of this include the loading and unloading of semitrailers in roll on-roll off vessels (ro-ro vessels); transfers of semitrailers in lorry terminals, as well as e.g. transfers of swap bodies from points of loading and unloading to stations where transport vehicles are waiting.
Traditionally these operations and transfers are carried out by means of so-called terminal tractors which are two-axle vehicles similar to lorries. These vehicles are expensive and of complicated build, and owing to their great length, less maneuverable. Especially in freight stations and industry's internal transports old tractors removed from actual road traffic have been reconditioned for short-range transfers. The only advantage of these vehicles lies in their relatively low price, in all other aspects they are inferior to the above mentioned terminal tractors.
Patent specification FI 50596 presents the principle of a single-axle tractor equipped with a gooseneck. The vehicle is not directly applicable to the use described here. Patent specification CH 533570 presents a transfer device with a 5th wheel for a semitrailer which transfer device grips the trailer by the kingpin. The device, however, is constructed in such a manner that in practice it is unable to control forces directed to it from the trailer to be transferred, for example forces directed to it upon braking seek to rotate it around the kingpin. The clearances of an ordinary 5th wheel locking and the dynamic shocks they enable damage either the pulling device or the kingpin upon sudden stress and make the transport a risky measure.